Sorry I couldn’t find it, but caffeine and coffee can have opposite effects on a person. Iirc caffeine making you sleepy is a symptom of ADHD or autism(it could be something else entirely, it was a long time ago I read the article) but was a very strong indicator of the thing in the article. This assumes it wasn’t a junk article, the acidity of the coffee apparently can have an effect on your metabolism depending on what else you put in it. Cinnamon apparently had a noticeable effect on the results.

Again apologies for not being able to locate it, but Ill update this if I do manage to find the one I remember. It was pre covid when I read it if that matters